Fallacy:
"How are we [society?] to decide what punishments are suitable [for crimes]?" (Danny Smith)
Response:
Nobody has the innate authority to "punish" (punishment is arbitrary harm for arbitrary acts, including peaceful ones). Justice belongs to the victim, not "society" or any third party, who have no right to interfere except as agents acting on behalf of victim or criminal.
See Justice page for more details on rational determination of just response to harm.